Charging and discharging mechanism of fuel cell system to secondary battery

Abstract

An electronic device includes a fuel cell providing a fuel voltage, a first switch, a rechargeable battery providing a battery voltage, a second switch, a relay, a driving circuit, and a controller. The first switch provides the fuel voltage to a first node according to a first control signal. The second switch is coupled to the first node, and charges the rechargeable battery with the fuel voltage according to a second control signal. The relay provides a voltage of the first node to the load according to the third control signal. The driving circuit generates the first control signal, the second control signal, and the third control signal according to a driving signal. The controller generates the driving signal according to the fuel voltage and the battery voltage.

What is claimed is: 
     
         1 . An electronic device, comprising:
 a fuel cell, providing a fuel voltage;   a first switch, providing the fuel voltage to a first node according to a first control signal;   a rechargeable battery, providing a battery voltage;   a second switch, coupled to the first node, wherein the second switch charges the rechargeable battery with the fuel voltage according to a second control signal;   a relay, providing a voltage of the first node to a load according to a third control signal;   a driving circuit, generating the first control signal, the second control signal, and the third control signal according to a driving signal; and   a controller, generating the driving signal according to the fuel voltage and the battery voltage.   
     
     
         2 . The electronic device as defined in  claim 1 , wherein when the controller determines that the fuel voltage exceeds the battery voltage and that the battery voltage does not exceed a first threshold voltage, the driving circuit turns on the first switch, the second switch, and the relay. 
     
     
         3 . The electronic device as defined in  claim 1 , wherein when the controller determines that the fuel voltage exceeds the battery voltage and that the battery voltage exceeds a first threshold voltage, the driving circuit turns on the first switch and the relay and turns off the second switch. 
     
     
         4 . The electronic device as defined in  claim 1 , wherein when the controller determines that the fuel voltage is less than the battery voltage, the driving circuit turns on the relay and turns off the first switch and the second switch, wherein the rechargeable battery powers the load through an additional diode of the second switch. 
     
     
         5 . The electronic device as defined in  claim 1 , wherein when the controller determines that the fuel voltage is equal to the battery voltage, the driving circuit turns on the first switch and the relay and turns off the second switch, wherein the rechargeable battery powers the load through an additional diode of the second switch and the fuel cell powers the load through the first switch. 
     
     
         6 . The electronic device as defined in  claim 1 , wherein when the controller determines that the fuel voltage exceeds a first threshold voltage, the driving circuit turns off the first switch. 
     
     
         7 . The electronic device as defined in  claim 1 , wherein when the controller determines that the fuel voltage exceeds a second threshold voltage, the driving circuit turns off the second switch. 
     
     
         8 . The electronic device as defined in  claim 1 , further comprising:
 a first voltage detection circuit, configured to detect the fuel voltage to generate a first voltage detection signal; and   a second voltage detection circuit, configured to detect the battery voltage to generate a second voltage detection signal, wherein the controller determines the fuel voltage and the battery voltage according to the first voltage detection signal and the second voltage detection signal.   
     
     
         9 . The electronic device as defined in  claim 1 , further comprising:
 a first current detector, coupled between the second switch and the rechargeable battery and configured to detect a battery current of the rechargeable battery to generate a first current detection signal.   
     
     
         10 . The electronic device as defined in  claim 9 , wherein when the controller determines that the fuel voltage exceeds the battery voltage and determines that a charging current of the rechargeable battery exceeds a maximum charging current according to the first current detection signal, the driving circuit turns on the first switch and the relay and periodically turns on the second switch. 
     
     
         11 . The electronic device as defined in  claim 9 , wherein when the controller determines that the fuel voltage exceeds the battery voltage and that a charging current of the rechargeable battery does not exceed a maximum charging current, the driving circuit turns on the first switch, the second switch, and the relay. 
     
     
         12 . The electronic device as defined in  claim 9 , wherein when the relay is turned off, the controller calculates state-of-charge of the rechargeable battery by using an open-circuit voltage method, wherein the controller further determines whether the battery current of the rechargeable battery exceeds a first current according to the first current detection signal. 
     
     
         13 . The electronic device as defined in  claim 12 , wherein when the battery current of the rechargeable battery exceeds the first current, the controller calculates the state-of-charge of the rechargeable battery by using an ampere-hour method, wherein when the battery current of the rechargeable battery does not exceed the first current, the controller calculates the state-of-charge of the rechargeable battery by using the open-circuit voltage method after a first predetermined period. 
     
     
         14 . A power-supply method adapted to an electronic device, wherein the electronic device comprises a fuel cell, a first switch, a second switch, a rechargeable battery, and a relay, wherein the first switch is coupled between the fuel cell and a first node, and the relay is coupled between the first node and a load, wherein the power-supply method comprises:
 detecting a fuel voltage of the fuel cell;   detecting a battery voltage of the rechargeable battery; and   turning on or off the first switch, the second switch, and the relay according to the fuel voltage and the battery voltage.   
     
     
         15 . The power-supply method as defined in  claim 14 , wherein the step of turning on or off the first switch, the second switch, and the relay according to the fuel voltage and the battery voltage further comprises:
 when the fuel voltage exceeds the battery voltage and the battery voltage does not exceed a first threshold voltage, turning on the first switch, the second switch, and the relay.   
     
     
         16 . The power-supply method as defined in  claim 14 , wherein the step of turning on or off the first switch, the second switch, and the relay according to the fuel voltage and the battery voltage further comprises:
 when the fuel voltage exceeds the battery voltage and the battery voltage exceeds a first threshold voltage, turning on the first switch and the relay and turning off the second switch.   
     
     
         17 . The power-supply method as defined in  claim 14 , wherein the step of turning on or off the first switch, the second switch, and the relay according to the fuel voltage and the battery voltage further comprises:
 when the fuel voltage is less than the battery voltage, turning on the relay and turning off the first switch and the second switch;   wherein the rechargeable battery powers the load through an additional diode of the second switch.   
     
     
         18 . The power-supply method as defined in  claim 14 , wherein the step of turning on or off the first switch, the second switch, and the relay according to the fuel voltage and the battery voltage further comprises:
 when the fuel voltage is equal to the battery voltage, turning on the first switch and the relay and turning off the second switch;   wherein the rechargeable battery powers the load through an additional diode of the second switch and the fuel cell powers the load through the first switch.   
     
     
         19 . The power-supply method as defined in  claim 14 , further comprising:
 detecting a charging current of the rechargeable battery;   wherein the step of turning on or off the first switch, the second switch, and the relay according to the fuel voltage and the battery voltage further comprises:
 when the fuel voltage exceeds the battery voltage and the charging current exceeds a maximum charging current, turning on the first switch and the relay and periodically turning on the second switch. 
   
     
     
         20 . The power-supply method as defined in  claim 19 , wherein the step of turning on or off the first switch, the second switch, and the relay according to the fuel voltage and the battery voltage further comprises:
 when the fuel voltage exceeds the battery voltage and the charging current does not exceed the maximum current, turning on the first switch, the second switch, and the relay.